Manufacture of bimetal articles



UNITED STATES PATENT OFFICE 1,936,222 MANUFACTURE OF BIMETAL ARTICLES Miner M. Austin, Waukegan, Ill., assignor to Fansteel Products Company, Inc., North Chicago, 111., a corporation of New York No Drawing. Application November 10, 1930 Serial No. 494,699

6 Claims. (Cl. 148-26) This invention relates in general to the manualuminum alloys, and nickel and silicon, and facture of bi-metal articles and has more particupartly of an ordinary or base metal forming a lar reference to fluxes for and a novel method. bond and backing for the first mentioned metal of frabricating difficultly solderable or fusible or alloy, and being integrally or intimately joined metals and of attaching such metals to other therewith.

metals. The union between the bond and backing ma- A primary object of the invention is to so join terial and the refractory metal or between two difiicultly solderable or fusible metals or to so atpieces of articles of a diflicultly fusible or soldertach two or more pieces or articles of metals, the able metal or alloy may be effected by any suit- 0 oxides or compounds of at least one of which are able means for attaching one metal to another refractory and resist wetting by ordinary brazing, u h a o d rin brazing or w d n Th artiwelding or soldering compounds that an intimate cles so formed combine the mechanical strength or in'egral metallic union will be effected, and non-corrodability 0f the one metal With the An important object of the invention is the at t v r s t y pp a f t th r.

15 provision of anovel method for integrally or inti- The surface fi of oxide on the e ac o y mately joining a, hard and tough metal such metals and the other hard metals and alloys alas tantalum, columbium, tungsten or alloys thereready mentioned, and their afilhity gaseous of with other metal impurities have heretofore precluded an integral Anoher important object of the inv nti n i m or intimate union between such metals and the 20 so treat such metals and alloys as nickel, silicon, base or ordinary m ta y s d ri r w ldi refractory metals and ferrous alloys thereof and Where the union Was made y p y heating high l in m n hr alloys t a halothe metals in contact with each other or rolling gen salt or compound as to render them combinahammering m W e in Contact.

ble with other metals or alloys which will proy invention contemplates vel method 25 vide a bond and backing'for the bi-plate article whereby tWO p s 0 articles of a difficultly fusias f d, ble or solderable metal or such a metal and an- A further important object of the invention is other metal are 50 treated that'the joining etal to treat tantalum with a non-fuming flux which or brazing, welding or soldering mpound atis chemically active with the oxides of tantalum tacks, p es 01' e ters into combination or 30 and which is impervious to gaseous impurities union with the entire surface 0 the diffiellli'ly whereby to adapt the tantalum for-use in th fusible or solderable metal or alloy and forms f ti of p t m articles by means 0f an intimate metallic union between such diflisoldering, brazing or otherwise securely an cultly fusible or solderable metals or between said tegrally attaching other metals. to the tantalum. metals and the base d ry metal.

35 Another important object of the invention is AS already mentioned, e a tery 0r difiithe provision of a halogen flux in which the recultly Solderehle t alleys Such, for e fractory metal oxides are soluble for use in 501- am a t u a alloys h f. sist dering base metals to refractory metals. Wetting by union With Ordinary S ,v

Another object of the invention is to provide brazing Welding compounds, O d y 40 an effective and simple method of joining diflimetals or alloys even when such metals or alloys cultly fusible or solderable metals such as the are heated to the molten Point in Order o e ct refractory metals by soldering, brazing or weldunion With t t t um. In Order to overing. come the foregoing objections whereby topro- Other objects and advantages will appear more vide a bi-metallic piece or article having the de- 45 fully from the following description, sirable physical, chemical and electrical proper- Briefly the present invention contemplates the ties of tantalum or the other refractory or hard manufacture of bi-metallic articles such as plates m ta s men iOned, I treat the Surface of the and wire or the fabrication of difficultly fusible t n lum wi h a h l fl x whi melts qui or solderable metals, the articles consisting of 1y and'which does not d c p fume b y 50 either a refractory or difllcultly solderable meal a temperatures above its melting Point t0 (118- or alloy fabricated by brazing, welding or solder- S l e t u f c OXideS and to Prevent gas ing, or consisting partly of a refractory metal or sorl y the tantalumalloy or any other metal or alloy which has here- Such a flux as the double potassium salts of tofore been found to'resist weting by ordinary tantalum fluoride, sodium aluminum fluoride, or

55 solders, such for example as chrome and high calcium chloride or fluor spar are very active chemically on the oxides of tantalum, columbium, chromium, aluminum and silicon.

Accordingly tantalum may be clipped in a fused bath of the halogen salt or compound contained in a nickel trough or vessel, and an ordinary solder such as silver solder or other molten metal or alloy spread or brought into contact with the surface of the tantalum, While the sheet is still beneath the molten flux. When so treated the metal or silver solder readily flows over the surface of the tantalum and makes an integral metallic union therewith thereby rendering the coated or plated tantalum capable of subsequent attachment by soldering or welding to other metals or to another piece or article of tantalum similarly treated.

Another method of utilizing these fluxes to form a bi-metallic piece or article including tantalum or any other refractory or hard metal is to prepare a fused bath of the desired backing and bonding metal such as copper, silver or gold covered with a fused layer of the flux and to lower or dip tantalum strips or wires through the fused flux and into the molten metal therebelow. It will, of course, be understood that where small surfaces are to be coated or plated the flux may be sprinkled over the surfaces and melted down with the flame.

On metals other than tantalum the salt may be sprinkled on the surface to be coated as described in the case of tantalum or it may be stuck in place with some suitable bonding material and melted by any known means.

In the fabrication of certain metals or alloys such as aluminum or alloys thereof, for example, there is some difllculty in casting due to the fact that thestock becomes oxidized beyond ordinary recovery as only a limited amount of the sprue and scrap can be added to the virgin metal. One method of improving this scrap is to melt the metal under a fluoride flux, for example calcium fluoride, sodium aluminum fluoride or a mixture thereof. These fluxes will hardly melt at the melting point of the alloy. Their melting point may be reduced, however, by the addition of potassium tantalum double fluoride. The invention, therefore, contemplates mixtures of the halogen salts or compounds to provide a flux having the desired melting point and providing the proper salt for dissolving the oxides from a fused metal bath.

It has been found that potassium tantalum double fluoride has a melting point of 700 C., while calcium fluoride or fiuor spar melts at 1378 C. The other fluxes or compounds mentioned above, have melting points ranging between the melting point of potassium tantalum double fluoride and calcium fluoride, making it possible to use potassium tantalum double fluoride alone as a low melting fluoride flux or in combination with any of the other fluxes to provide a halogen compound or salt having the 1 desired melting point.

When it is attempted to join tantalum to a backing and bond metal without the use of one of the fluxes described above the backing or bonding metal gathers in globules on the surface of l the tantalum and upon cooling is found not to adhere.

The bi-metallic pieces or articles may be reduced in section as by rolling, swaging, drawing or otherwise working without changing the relative proportion of cross section of the respective metals or alloys and without disturbing the tenacious adherence of the union therebetween. It is to be understood that the invention contemplates the use of any halogen salt or compound 9 having a solvent action on the oxides of the hard or refractory metal, as distinguished from such fluxes as borax and soda and oxygen containing fluxes which are not effective in causing tantalumv or the other refractory metals mentioned above to adhere to ordinary or base metals, to one another, or to themselves.

While I have described a specific embodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details set forth but desire to avail myself of all changes within the scope of the appended claims.

I claim:

1. A flux for use in joining difiicultly solderable metals which comprise potassium tantalum double fluoride.

2. A flux for use in joining diflicultiy solderable metals, comprising potassium tantalum double fluoride and another halogen salt having a higher melting point than said fluoride.

3. A flux comprising a fused mixture of potassium tantalum double fluoride, and a halogen salt having a higher melting point than said potassium tantalum double fluoride.

4. A flux comprising a halide having a melting point of from 700" C. to 1378 C. and potassium tantalum double fluoride.

5. A flux comprising a mixture of potassium tantalum double fluoride and another fluoride, substantially stable at temperatures above the melting point of said mixture.

6. A flux comprising a quietly meltable mixture of a halide having a melting point above 700 C. and potassium tantalum double fluoride.

MINER M. AUSTIN. 

